title: Characterisation of an engineered trastuzumab IgE antibody and effector cell mechanisms targeting HER2/neu-positive tumour cells.
abstract: Trastuzumab (Herceptin), a humanized IgG1 antibody raised against the human epidermal growth factor receptor 2 (HER2/neu), is the main antibody in clinical use against breast cancer. Pre-clinical evidence and clinical studies indicate that trastuzumab employs several anti-tumour mechanisms that most likely contribute to enhanced survival of patients with HER2/neu-positive breast carcinomas. New strategies are aimed at improving antibody-based therapeutics like trastuzumab, e.g. by enhancing antibody-mediated effector function mechanisms. Based on our previous findings that a chimaeric ovarian tumour antigen-specific IgE antibody showed greater efficacy in tumour cell killing, compared to the corresponding IgG1 antibody, we have produced an IgE homologue of trastuzumab. Trastuzumab IgE was engineered with the same light- and heavy-chain variable-regions as trastuzumab, but with an epsilon in place of the gamma-1 heavy-chain constant region. We describe the physical characterisation and ligand binding properties of the trastuzumab IgE and elucidate its potential anti-tumour activities in functional assays. Both trastuzumab and trastuzumab IgE can activate monocytic cells to kill tumour cells, but they operate by different mechanisms: trastuzumab functions in antibody-dependent cell-mediated phagocytosis (ADCP), whereas trastuzumab IgE functions in antibody-dependent cell-mediated cytotoxicity (ADCC). Trastuzumab IgE, incubated with mast cells and HER2/neu-expressing tumour cells, triggers mast cell degranulation, recruiting against cancer cells a potent immune response, characteristic of allergic reactions. Finally, in viability assays both antibodies mediate comparable levels of tumour cell growth arrest. These functional characteristics of trastuzumab IgE, some distinct from those of trastuzumab, indicate its potential to complement or improve upon the existing clinical benefits of trastuzumab.
authors.affiliation: Cutaneous Medicine and Immunotherapy Unit, St. John's Institute of Dermatology, Division of Genetics and Molecular Medicine, King's College London School of Medicine, Guy's Tower, Guy's Hospital, London, UK.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Karagiannis
authors.forename: Josef
authors.initials: J
authors.lastname: Singer
authors.forename: James
authors.initials: J
authors.lastname: Hunt
authors.forename: Samuel K E
authors.initials: SK
authors.lastname: Gan
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Rudman
authors.forename: Diana
authors.initials: D
authors.lastname: Mechtcheriakova
authors.forename: Regina
authors.initials: R
authors.lastname: Knittelfelder
authors.forename: Tracy R
authors.initials: TR
authors.lastname: Daniels
authors.forename: Philip S
authors.initials: PS
authors.lastname: Hobson
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Beavil
authors.forename: James
authors.initials: J
authors.lastname: Spicer
authors.forename: Frank O
authors.initials: FO
authors.lastname: Nestle
authors.forename: Manuel L
authors.initials: ML
authors.lastname: Penichet
authors.forename: Hannah J
authors.initials: HJ
authors.lastname: Gould
authors.forename: Erika
authors.initials: E
authors.lastname: Jensen-Jarolim
authors.forename: Sophia N
authors.initials: SN
authors.lastname: Karagiannis
mesh_terms: D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D061067:Antibodies, Monoclonal, Humanized; D000920:Antibody-Dependent Cell Cytotoxicity / Q000187:drug effects / Q000276:immunology*; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000276:immunology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology*; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010587:Phagocytosis; D015202:Protein Engineering; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology*; D017455:Receptors, IgE / Q000276:immunology / Q000378:metabolism; D000068878:Trastuzumab
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D007073:Immunoglobulin E; D018719:Erb-b2 Receptor Tyrosine Kinases; D017455:Receptors, IgE; D000068878:Trastuzumab; C475664:FCER1A protein, human